Roofing tiles used in up to 5 million homes in Japan -- 20 percent of the total -- are believed to contain asbestos, tile makers said Saturday.
The tiles include those made by Kubota Corp. between 1961 and 2001 and by the Matsushita Electric Works group between 1971 and 2003.
Asbestos, a naturally occurring mineral fiber, is known to cause health problems, including lung cancer and mesothelioma, a rare form of cancer. Experts say the roofing tiles can scatter asbestos when damaged or demolished.
The report could force the government and housing industries to take further preventive measures.